Mobile robot and method of tracking mobile robot

ABSTRACT

A mobile robot includes a mobile robot body, a drawing unit provided at the mobile robot body and including a marker configured to draw a travel locus of the mobile robot on a travel plane, and a detector provided at the mobile robot body and configured to detect the travel locus drawn by the drawing unit. The mobile robot travels along the travel locus detected by the detector.

BACKGROUND OF THE INVENTION Technical Field

The present disclosure relates to a mobile robot configured to executetracking control of a single or a plurality of mobile robots and amethod of tracking a mobile robot.

Description of the Related Art

A technique for tracking control of a mobile robot includes a typicallyknown method of detecting a target object to be tracked (such as aperson or a mobile object) with use of a laser range scanner disposed ata front portion of the mobile robot and tracking the target object.

This method fails to enable distinction of the target object. In a caseof tracking one of a plurality of persons, the person to be tracked maybe lost and a person different from the tracking target may be tracked.

Assume another case of executing tracking control in accordance with themethod described above with a plurality of mobile robots in asingle-line formation. When a tracked robot turns around an obstacle orat a corner, tracking robots turn at the respective points. The mobilerobot closer to the end of the line has a travel locus too close to theobstacle or the corner and thus highly possibly runs into the obstacleor the corner.

This problem can be solved by executing tracking control along anidentical trajectory of causing the plurality of tracking mobile robotsto travel along the locus of the tracked mobile robot at the forefrontof the line (refer to Patent Document 1: Japanese Unexamined PatentApplication Publication No. 2005-46926).

Such tracking control along the identical trajectory requires each ofthe mobile robots in the formation to accurately recognize the travellocus of the tracked mobile robot at the forefront of the formation anda current own position. The mobile robots accordingly need to moveautonomously.

A technique of recognizing an own position of an autonomously mobilerobot includes a typical method of comparing a preliminarily preparedmap of landmarks with positions of the landmarks acquired by a laserrange scanner.

FIG. 38 is an outline view according to Patent Document 1, of trackingcontrol along an identical trajectory. A tracked mobile robot 20 and atracking mobile robot 50 each include a laser range scanner 40 and acommunicator 30. Assume that these robots 20 and 50 travel in a knownenvironment of which an environmental map is prepared. The trackedmobile robot 20 moves autonomously. The mobile robot 20 recognizes anown position with use of the laser range scanner 40 and with referenceto the environmental map, and teaches the tracking mobile robot 50 asneeded with use of the communicator 30 a locus 60 of the recognized ownposition. The tracking mobile robot 50 tracks the taught locus 60 of theposition of the tracked mobile robot 20 while sequentially recognizingan own position with use of the laser range scanner 40.

This method requires a landmark like a wall in a travel environment forrecognition of the own position of the tracking mobile robot 50. Thetracking mobile robot 50 fails to recognize the own position in a broadspace including no wall or the like. In a case where each autonomouslymobile robot loading cargo or a person reaches a destination (e.g. aboarding gate) in a large facility such as an air terminal and scatteredautonomously mobile robots are then to be collected at one site, themobile robots have difficulty in recognizing own positions because ofthe large facility. Tracking control along an identical trajectorycannot be executed in this case.

SUMMARY

The present disclosure has been achieved in view of such a conventionalissue, and an object thereof is to provide a mobile robot configured toexecute tracking control along an identical trajectory of a plurality ofmobile robots even in an environment like a broad space including nowall or the like, where the mobile robots are inhibited from recognizingown positions, and provide a method of tracking the mobile robot.

One non-limiting and exemplary embodiment of the present disclosureprovides a mobile robot comprising:

a mobile robot body;

a drawing unit provided at the mobile robot body and including a markerconfigured to draw a travel locus of the mobile robot on a travel plane;

a detector provided at the mobile robot body and configured to detectthe travel locus drawn by the drawing unit;

a travel driving unit configured to drive to move the mobile robot body;and

a drive controller configured to drive control the travel driving unitsuch that the mobile robot body travels along the travel locus detectedby the detector.

It should be noted that general or specific embodiments may beimplemented as a system (or an apparatus), a method, an integratedcircuit, a computer program, a storage medium, or any selectivecombination thereof.

Any one of the aspects of the present disclosure enables, in trackingtravel of the plurality of mobile robots, the drawing unit in the mobilerobot at the forefront of the line to draw the travel locus on thetravel plane, enables the detector in the tracking mobile robot todetect the drawn travel locus, and enables the tracking mobile robot totravel along the detected travel locus. Accordingly, tracking controlalong an identical travel locus of a plurality of mobile robots isachieved even in an environment like a broad space including no wall orthe like where the mobile robots are inhibited from recognizing ownpositions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic explanatory view from the top of a mobile robotaccording to a first embodiment of the present disclosure;

FIG. 2 is a schematic sectional view from a side of the mobile robotaccording to the first embodiment of the present disclosure;

FIG. 3A is a plan view from the top of the mobile robot, of a drawingunit, according to the first embodiment of the present disclosure;

FIG. 3B is a perspective view from the bottom of the mobile robot, ofthe drawing unit, according to the first embodiment of the presentdisclosure;

FIG. 3C is a block diagram of a travel plane determiner of the mobilerobot according to the first embodiment of the present disclosure;

FIG. 3D is an explanatory view of a particle discharge mechanismexemplifying the drawing unit of the mobile robot according to the firstembodiment of the present disclosure;

FIG. 4A is a plan view from the top of the mobile robot, of a detector,according to the first embodiment of the present disclosure;

FIG. 4B is a perspective view from the bottom of the mobile robot, ofthe detector, according to the first embodiment of the presentdisclosure;

FIG. 4C is a block diagram of the detector having an exemplaryconfiguration, of the mobile robot according to the first embodiment ofthe present disclosure;

FIG. 4D is a block diagram of the detector having another exemplaryconfiguration, of the mobile robot according to the first embodiment ofthe present disclosure;

FIG. 4E is an explanatory view depicting an image (a) captured by acamera in FIG. 4D and data (b) obtained by binarizing the image;

FIG. 4F is a lower-side perspective view depicting an internal structureof the detector in FIG. 4B, excluding a cover and the like;

FIG. 4G is a graph indicating an exemplary relationship betweenreflectance and a sensor position;

FIG. 5 is a positional relationship diagram of the drawing unit and thedetector of the mobile robot according to the first embodiment of thepresent disclosure;

FIG. 6 is an explanatory view depicting a state where mobile robots aredisposed in a collection system according to the first embodiment of thepresent disclosure;

FIG. 7 is a plot plan of the mobile robots at a collection site in thecollection system according to the first embodiment of the presentdisclosure;

FIG. 8 is a positional relationship diagram of the mobile robotsdisposed in the vicinity of each boarding gate in the collection systemaccording to the first embodiment of the present disclosure;

FIG. 9A is a collection flowchart of basic behavior of the collectionsystem according to the first embodiment of the present disclosure;

FIG. 9B is a specifically exemplified collection flowchart for thecollection system according to the first embodiment of the presentdisclosure;

FIG. 10 is a state diagram of the collection flow shown in FIG. 9Baccording to the first embodiment of the present disclosure (depictingmovement from in the vicinity of a boarding gate A to in the vicinity ofa boarding gate B);

FIG. 11 is a state diagram of the collection flow according to the firstembodiment of the present disclosure (depicting activation of the mobilerobots in the vicinity of the boarding gate B);

FIG. 12 is a state diagram of the collection flow according to the firstembodiment of the present disclosure (depicting movement from in thevicinity of the boarding gate B to in the vicinity of a boarding gateC);

FIG. 13 is a state diagram of the collection flow according to the firstembodiment of the present disclosure (depicting activation of the mobilerobots in the vicinity of the boarding gate C);

FIG. 14 is a state diagram of the collection flow according to the firstembodiment of the present disclosure (depicting movement from in thevicinity of the boarding gate C to the collection site);

FIG. 15 is a state diagram of the collection flow according to the firstembodiment of the present disclosure (depicting stopped positions of themobile robots at the collection site);

FIG. 16 is a state diagram of the collection flow according to the firstembodiment of the present disclosure (depicting movement of a firstmobile robot from the collection site to a storage site);

FIG. 17 is a state diagram of the collection flow according to the firstembodiment of the present disclosure (depicting movement of a secondmobile robot from the collection site to the storage site);

FIG. 18 is a state diagram of the collection flow according to the firstembodiment of the present disclosure (depicting movement of a sixthmobile robot from the collection site to the storage site);

FIG. 19 is a schematic explanatory view from the top of a mobile robotaccording to a second embodiment of the present disclosure;

FIG. 20 is a schematic sectional view from a side of the mobile robotaccording to the second embodiment of the present disclosure;

FIG. 21A is a plan view from the top of the mobile robot, of an eraser,according to the second embodiment of the present disclosure;

FIG. 21B is a perspective view from the bottom of the mobile robot, ofthe eraser, according to the second embodiment of the presentdisclosure;

FIG. 21C is an explanatory view depicting a configuration of a suckingdevice provided as the eraser in the mobile robot;

FIG. 22 is a positional relationship diagram of a drawing unit, adetector, and the eraser of the mobile robot according to the secondembodiment of the present disclosure;

FIG. 23 is an explanatory view depicting a positional distribution stateof mobile robots in a collection system according to the secondembodiment of the present disclosure;

FIG. 24 is an arrangement plan of the mobile robots at a collection sitein the collection system according to the second embodiment of thepresent disclosure;

FIG. 25 is a positional relationship diagram of the mobile robotdisposed in the vicinity of each boarding gate in the collection systemaccording to the second embodiment of the present disclosure;

FIG. 26A is a collection flowchart of basic behavior of the collectionsystem according to the second embodiment of the present disclosure;

FIG. 26B is a specifically exemplified collection flowchart for thecollection system according to the second embodiment of the presentdisclosure;

FIG. 27 is a state diagram of the collection flow shown in FIG. 26Baccording to the second embodiment of the present disclosure (depictingmovement from in the vicinity of a boarding gate A to in the vicinity ofa boarding gate B);

FIG. 28 is a state diagram of the collection flow according to thesecond embodiment of the present disclosure (depicting activation of themobile robots in the vicinity of the boarding gate B);

FIG. 29 is a state diagram of the collection flow according to thesecond embodiment of the present disclosure (depicting movement from inthe vicinity of the boarding gate B to in the vicinity of a boardinggate C);

FIG. 30 is a state diagram of the collection flow according to thesecond embodiment of the present disclosure (depicting activation of themobile robots in the vicinity of the boarding gate C);

FIG. 31 is a state diagram of the collection flow according to thesecond embodiment of the present disclosure (depicting movement from inthe vicinity of the boarding gate C to the collection site);

FIG. 32 is a state diagram of the collection flow according to thesecond embodiment of the present disclosure (depicting stopped positionsof the mobile robots at the collection site);

FIG. 33 is a state diagram of the collection flow according to thesecond embodiment of the present disclosure (depicting movement of afirst mobile robot from the collection site to a storage site);

FIG. 34 is a state diagram of the collection flow according to thesecond embodiment of the present disclosure (depicting movement of asecond mobile robot from the collection site to the storage site);

FIG. 35 is a state diagram of the collection flow according to thesecond embodiment of the present disclosure (depicting movement of asixth mobile robot from the collection site to the storage site);

FIG. 36 is a schematic explanatory view from the top of a mobile robotaccording to a third embodiment of the present disclosure;

FIG. 37 is a collection flowchart for a collection system according tothe third embodiment of the present disclosure; and

FIG. 38 is an outline view of tracking control along an identical travellocus of a plurality of mobile robots according to a conventionalmethod.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the present disclosure will now be described belowwith reference to the accompanying drawings. Identical constituentelements will be denoted by identical reference signs. The drawingsschematically depict their main constituent elements for easierunderstanding.

First Embodiment

A mobile robot according to the first embodiment of the presentdisclosure will initially be described with reference to the drawings.FIG. 1 is a schematic explanatory view from the top of a mobile robot100 according to the first embodiment of the present disclosure. Themobile robot 100 at least includes a mobile robot body 1, a drawing unit6, a detector 7, a travel driving unit 15, and a controller 14 includinga drive controller 10.

The drawing unit 6 includes a marker 6 b configured to draw a travellocus 5 of the mobile robot 100 on a travel plane 19 of the mobile robot100.

The detector 7 detects the travel locus 5 drawn on the travel plane 19by the drawing unit 6.

The travel driving unit 15 is embodied by a driving device like a motor,and is configured to drive to positively and negatively rotate a pair ofdriving wheels 2 independently from each other. The travel driving unit15, the pair of driving wheels 2, and a pair of trailing wheels 3configure a travel driving device.

More specifically, the mobile robot body 1 of the mobile robot 100further includes a distance sensor 4 and a travel plane determiner 21.

The distance sensor 4 measures a distance to a position ahead of themobile robot 100, specifically, to an obstacle in a travel directionthereof.

The travel plane determiner 21 detects a material for the travel plane19 to determine a type of the travel plane 19.

The respective constituent elements will be described in detail below.

The distance sensor 4 is disposed at the front or the like of the mobilerobot body 1 and is configured to measure a distance to an obstacle inthe travel direction of the mobile robot 100. The controller 14 receivesmeasurement information. The controller 14 drive controls the traveldriving unit 15 in accordance with the measurement information, to allowthe mobile robot 100 to travel while avoiding the obstacle. The distancesensor 4 is exemplified by an infrared distance sensor.

The controller 14 is connected to the drawing unit 6 and the detector 7,and independently controls drawing by the drawing unit 6 and detectionby the detector 7. The controller 14 includes a calculator 9 and thedrive controller 10.

The calculator 9 calculates the travel locus 5 to be tracked inaccordance with movement trace information on the travel locus 5detected by the detector 7 and acquired from the detector 7.

The drive controller 10 executes tracking control by causing the traveldriving unit 15 to drive control the pair of driving wheels 2 to achievemovement along the travel locus 5 calculated by the calculator 9.

The drive controller 10 drive controls the travel driving unit 15, thedetector 7, and the drawing unit 6, independently from one another.

The mobile robot 100 can further include an operation unit 16 at leasthaving a steering wheel and an operation panel used for steering amobile robot 101 to a desired destination by a collector 11 boarding themobile robot 101. The travel driving unit 15 can alternatively bedrive-controlled via the drive controller 10 of the controller 14 inaccordance with an operation command inputted to the operation panel ofthe operation unit 16 by the collector 11.

FIG. 2 is a schematic sectional view from a side of the mobile robot100. The drawing unit 6 is provided at the mobile robot body 1 to behigh enough to draw the travel locus 5 directly on the travel plane 19.The detector 7 is provided at the mobile robot body 1 to be high enoughto detect the travel locus 5 drawn on the travel plane 19 by the drawingunit 6. The detector 7 is accordingly disposed ahead of the drawing unit6 in the travel direction of the mobile robot 100.

FIGS. 3A and 3B are detailed views of the drawing unit 6. FIG. 3A is aplan view from the top of the mobile robot 100, of the drawing unit 6,whereas FIG. 3B is a perspective view from the bottom of the mobilerobot 100, of the drawing unit 6.

The drawing unit 6 includes an expandable portion 6 a configured to beaxially expandable (e.g. vertically in FIG. 3B), the marker 6 b fixed ata distal end (e.g. the lower end in FIG. 3B) of the expandable portion 6a and having a projecting end soaking paint, and a drawing unit driver 6g like a motor configured to axially move the marker 6 b via theexpandable portion 6 a and drive-controlled by the drive controller 10.

When the drawing unit 6 is activated, the drawing unit driver 6 g like amotor lowers the marker 6 b to extend the expandable portion 6 a axiallydownward and the lower end of the marker 6 b comes into direct contactwith the travel plane 19 as a travel plane, so that the paint of themarker 6 b is directly applied to the travel plane 19 as the travellocus 5. The travel locus 5 is exemplified by a belt-like straight linehaving a predetermined width of about several centimeters.

When the mobile robot 100 stops or the drawing unit 6 stops drawing, thedrawing unit driver 6 g like a motor raises the marker 6 b to contractthe expandable portion 6 a and prevent the marker 6 b from directlycontacting the travel plane 19.

Examples of the paint to be applied to the travel plane 19 include paintto be detected only by the detector 7. More specific examples of thepaint include paint that shines only when irradiated with black light orthe like. Such specific examples of the paint include black light inkthat has milky white color inapparent even when applied withoutirradiation with black light and apparently changes in color from milkywhite into red, green, or blue with irradiation with black light. Suchpaint applied to the travel plane 19 will conveniently be invisible topersons except for the mobile robot 100. The above method includesdrawing the travel locus 5 with use of paint, which can be replaced withcolored powder, a tape, or the like.

The method of drawing the travel locus 5 can be selected after thetravel plane determiner 21 detects the material for the travel plane 19and determines the type of the travel plane 19.

As shown in FIG. 3C, the travel plane determiner 21 includes acomparator 21 a, a material determiner 21 b, and a memory 21 c. Thememory 21 c exemplarily stores a surface image of a hard tile and asurface image of a rug or a carpet, as well as information on paint tobe applied to the hard tile and particles to be applied to the rug orthe carpet and being substantially as large as lime. The comparator 21 areceives an image captured by a camera exemplifying an imaging deviceconfiguring the detector 7. The comparator 21 a compares the receivedimage with the image stored in the memory 21 c. According to anexemplary comparison method, the comparator 21 a compares the receivedimage with the image stored in the memory 21 c in accordance withpattern matching. The material determiner 21 b receives a result of thecomparison. The material determiner 21 b determines whether the receivedimage relates to a hard tile, or a rug or a carpet, in accordance withthe result of the comparison by the comparator 21 a, acquiresinformation on the paint or the particles corresponding to thedetermined material in accordance with the information stored in thememory 21 c, and outputs, to the drawing unit 6, the acquiredinformation on the paint or the particles as information on the materialto be used for drawing.

For example, in a case where the material determiner 21 b determinesthat the travel plane 19 is a hard tile or the like, the drawing unit 6adopts the paint. In another case where material determiner 21 bdetermines that the travel plane 19 is a rug or a carpet, the drawingunit 6 draws the travel locus 5 by scattering the particlessubstantially as large as lime on the travel plane 19, instead ofapplying paint that is hard to be removed from the rug or the carpet.Examples of the particles substantially as large as lime includeparticles having the maximum diameter more than 0 μm and equal to orless than 10 μm.

The information on the travel plane 19 stored in the memory 21 c isexemplified by the two types. The present embodiment is not limited tothese types, but the memory 21 c can alternatively store a preliminarilycaptured image of the travel plane 19 to be traveled by the mobile robot100 and a drawing material to be applied to the travel plane 19corresponding to the image, associating the image with the drawingmaterial.

Examples of a device configured to scatter the particles substantiallyas large as lime include a particle discharge mechanism 70 as shown inFIG. 3D. The drawing unit 6 in FIGS. 3A and 3B may be referred as afirst drawing unit, whereas the particle discharge mechanism 70 may bereferred as a second drawing unit.

The particle discharge mechanism 70 includes a driving unit 71, anencoder 72, a particle storage tank 73, and a discharge switchingcontroller 74. The driving unit 71 positively or negatively rotates adriving motor 71 b to positively or negatively rotate a drive shaft 71 aas a screw shaft so as to move the particle storage tank 73 screwed tothe drive shaft 71 a forward or backward along the drive shaft 71 a. Theparticle storage tank 73 stores the particles and has a lower openingclosed by a shutter 73 a. Under the control of the discharge switchingcontroller 74, the shutter 73 a rotates positively or negatively about arotary shaft of a motor 73 b rotating positively or negatively, to openor close the lower opening of the particle storage tank 73. When thedrawing unit 6 starts drawing, the discharge switching controller 74rotates the shutter 73 a to open the lower opening to allow theparticles to drop from the particle storage tank 73 for drawing.

The travel driving unit 15 includes an encoder 15 e that detectsrotational speed of a motor 15 m to detect travel speed of the mobilerobot 100. The discharge switching controller 74 controls an openingdegree of the shutter 73 a such that particle density of the travellocus 5 on the travel plane 19 is not largely varied in accordance withthe travel speed.

FIGS. 4A and 4B are detailed views of the detector 7. FIG. 4A is a planview from the top of the mobile robot 100, of the detector 7, whereasFIG. 4B is a perspective view from the bottom of the mobile robot 100,of the detector 7. FIG. 4C is a block diagram of the detector having anexemplary configuration, whereas FIG. 4D is a block diagram of thedetector having another exemplary configuration. FIG. 4E depicts animage (a) captured by the camera and data (b) obtained by binarizing theimage.

The detector 7 includes a plurality of paint detection sensors 7 a and adeterminer 7 d as exemplarily shown in FIG. 4C. The paint detectionsensors 7 a each include a light emitter 7 b and a light receiver 7 c.The paint detection sensor 7 a irradiates the travel plane 19 with lightfrom the light emitter 7 b, causes the light receiver 7 c to receivelight reflected at the travel plane 19, and the determiner 7 ddetermines whether or not the travel plane 19 has the travel locus 5 inaccordance with intensity of the light received by the light receiver 7c. The light emitter 7 b is exemplified by an LED black light configuredto emit black light. The light receiver 7 c is configured by a photoreflector and detects the black light emitted from the light emitter 7b. The determiner 7 d determines that the travel plane 19 has the travellocus 5 in accordance with a result of the detection by the lightreceiver 7 c. The determiner 7 d can determine that the travel plane 19has the travel locus 5 in a case where the travel plane 19 and thetravel locus 5 have a difference in color value equal to or more than athreshold and the travel locus 5 is linear. The plurality of paintdetection sensors 7 a is exemplarily aligned in series to cross, forexample, to be perpendicular to, the travel direction of the mobilerobot 100 or an extending direction of the travel locus 5. Provision ofthe plurality of the paint detection sensors 7 a enables calculation ofa relative position of the mobile robot 100 to the travel locus 5. Thedrive controller 10 in the mobile robot 100 executes tracking control inaccordance with information on the relative position.

FIG. 4F is a lower-side perspective view depicting an internal structureof the detector 7 in FIG. 4B, excluding a cover and the like. As shownin FIG. 4F, the paint detection sensors 7 a each irradiate the travelplane 19 with light 17 e from a photodiode 17 b functioning as the lightemitter 7 b and causes a photo reflector 17 c functioning as the lightreceiver 7 c to receive light 17 d reflected at the travel plane 19, andthe determiner 7 d determines whether or not the travel plane 19 has thetravel locus 5 in accordance with reflectance of the light 17 d receivedby the photo reflector 17 c. FIG. 4G exemplarily indicates arelationship between the reflectance and positions of the sensors 7 a.In a case where there are provided seven sensors 7 a as shown in FIG.4F, the determiner 7 d calculates a relative position of the travellocus to the mobile robot 100 in accordance with the position of thefourth sensor 7 a having the highest reflectance as indicated in FIG.4G. Assume that the fourth sensor 7 a in the center in the widthdirection of the seven sensors 7 a in the travel direction of the mobilerobot 1 has a relative position of zero. The determiner 7 d calculates adegree of displacement, from the fourth sensor 7 a, of the sensor 7 ahaving detected the travel locus 5. For example, when a sensor 7 adetecting the travel locus 5 is the fourth sensor 7 a with respect tothe fourth sensor 7 a in the center, the determiner 7 d determines thatthe relative position is zero and the mobile robot 100 continuouslytravels straight. In a case where the third or second sensor 7 a detectsthe travel locus 5, the determiner 7 d determines that the relativeposition is displaced by one or two to the left from the fourth sensor 7a, and the travel driving unit 15 is controlled to turn the mobile robot100 to the right. In another case where the fifth or sixth sensor 7 adetects the travel locus 5, the determiner 7 d determines that therelative position is displaced by one or two to the right, and thetravel driving unit 15 is controlled to turn the mobile robot 100 to theleft.

The plurality of paint detection sensors in the detector 7 can bereplaced with a wide-field imaging device. Examples of the imagingdevice include a camera 7 e. As shown in FIG. 4D, the detector 7alternatively may include the camera 7 e, a binarizer 7 f, and adeterminer 7 g. When the binarizer 7 f binarizes an image captured bythe camera 7 e, the travel plane 19 and the travel locus 5 can bedistinguished from each other in color, as shown in FIG. 4E. Forexample, in a case where the paint or the particles used for drawing thetravel locus 5 are lighter in color than the travel plane 19, thedeterminer 7 g can determine an area in the lighter color as the travellocus 5. Specifically, assuming that the image (a) in FIG. 4E iscaptured by the camera 7 e, the data (b) in FIG. 4E is obtained bybinarizing the image (a). In this case, the determiner 7 g can determinethe area of a white thick line at the center of the image as the travellocus 5.

FIG. 5 depicts a positional relationship among the distance sensor 4,the drawing unit 6, and the detector 7 provided at the mobile robot body1. The distance sensor 4 is configured to measure a distance to anobstacle in the travel direction of the mobile robot 100, and is thusdisposed at the front surface of the mobile robot body 1. The drawingunit 6 and the detector 7 are disposed in series in the mobile robotbody 1 in the travel direction of the mobile robot 100. The detector 7is disposed ahead of the drawing unit 6 in this case.

A first mobile robot 100 and a second mobile robot 100 accordingly havean identical travel locus. The mobile robots 100 can travel on a narrowpassage as wide as the single mobile robot 100. Assume that the drawingunit 6 and the detector 7 are disposed apart from each other by adistance Y. The distance Y will be referred to later.

A method of tracking the mobile robot 100 will be described next byexemplifying an air terminal requiring tracking along an identical locusof the mobile robots 100. Specifically described is a collection systemS100 adopting tracking control of six mobile robots 100. For conveniencein the description, the six mobile robots 100 will be denoted by a firstmobile robot 101, a second mobile robot 102, a third mobile robot 103, afourth mobile robot 104, a fifth mobile robot 105, and a sixth mobilerobot 106.

The collection system S100 for the mobile robots 100 includes the firstmobile robot 101, the second mobile robot 102, the third mobile robot103, the fourth mobile robot 104, the fifth mobile robot 105, and thesixth mobile robot 106.

Briefly, in order to gather the two mobile robots 100 disposed in thevicinity of each of boarding gates A to C (in other words, locations T1to T3) shown in FIG. 6 to be referred to later to form a mobile robotline and then collect the mobile robot line at a single collection site(in other words, a location T4), one of the mobile robots 100 disposedat the location T1 as the boarding gate A most distant from thecollection site T4 is assumed to be at the forefront of the mobile robotline. The mobile robots 100 disposed at the locations T2 and T3 as theboarding gates B and C track a single travel locus drawn by the mobilerobot 100 at the forefront, and all the mobile robots 100 in the mobilerobot line are collected at the collection site T4.

FIG. 6 is a view depicting a state where the six mobile robots 101 to106 are disposed at the locations T1 to T3 in the collection systemS100. The two mobile robots, namely, the first mobile robot 101 and thesecond mobile robot 102 are disposed next to each other at the locationT1 as the boarding gate A and are directed identically in theanteroposterior direction. The first mobile robot 101 is disposed aheadin the travel direction and the second mobile robot 102 is disposedbehind in the travel direction of the first mobile robot 101. Similarly,the two mobile robots, namely, the third mobile robot 103 and the fourthmobile robot 104 are disposed next to each other at the location T2 asthe boarding gate B and are directed identically in the anteroposteriordirection. The third mobile robot 103 is disposed ahead in the traveldirection and the fourth mobile robot 104 is disposed behind in thetravel direction of the third mobile robot 103. Similarly, the twomobile robots, namely, the fifth mobile robot 105 and the sixth mobilerobot 106 are disposed next to each other at the location T3 as theboarding gate C and are directed identically in the anteroposteriordirection. The fifth mobile robot 105 is disposed ahead in the traveldirection and the sixth mobile robot 106 is disposed behind in thetravel direction of the fifth mobile robot 105.

FIG. 7 is a view of the collection site T4 for the six mobile robots 101to 106 in the collection system S100. The mobile robots 101 to 106 arecollected sequentially at the collection site T4 to form a single linesuch that the first mobile robot 101 is disposed at the forefront (e.g.the lower end in FIG. 7) in the travel direction.

FIG. 8 is a view depicting a positional relationship of the mobilerobots 101 to 106 disposed at the locations T1 to T3 as the boardinggates. A distance from the rear end of the mobile robot 101, 103, or 105disposed ahead at the location to the front end of the mobile robot 102,104, or 106 disposed behind will be referred to as an inter-robotdistance, and the permissible maximum value of the inter-robot distancewill be referred to as a maximum permissible inter-robot distance.Assume that a distance X is obtained by adding a distance D1 from thedrawing unit 6 included in each of the mobile robots 101 to 106 to therear end of the mobile robot and a maximum permissible inter-robotdistance D2.

Described next is a collection flow of the collection system S100 for aplurality of mobile robots 100 executing tracking travel in a singleline. A specific example thereof will be described after description ofbasic behavior. FIG. 9A is a flowchart depicting the basic collectionbehavior.

Initially in step S40, the drive controller 10 determines whether or notthe mobile robot 100 executing tracking travel in a single line of aplurality of mobile robots 100 is at the forefront of the line. Thisdetermination can be made by the collector 11 who manipulates theoperation unit 16 to inform the drive controller 10 that this mobilerobot 100 is at the forefront of the line. The drive controller 10 canalternatively determine that this mobile robot 100 is at the forefrontof the line when the distance sensor 4 detects that there is no othermobile robot 100 ahead of this mobile robot 100 for a predeterminedperiod. The drive controller 10 can still alternatively determine thatthis mobile robot 100 is at the forefront of the line in a case wherethe detector 7 detects no travel locus 5 even after this mobile robot100 moves for a predetermined period or by a predetermined distance.

The flow proceeds to step S41 if the drive controller 10 determines thatthis mobile robot 100 is at the forefront of the line. The flow proceedsto step S42 if the drive controller 10 determines that this mobile robot100 is not at the forefront of the line.

Subsequently, in step S41, since the mobile robot 100 is at theforefront of the line, the drive controller 10 controls to activate thedrawing unit 6 in the mobile robot 100 at the forefront of the line sothat the drawing unit 6 starts drawing the travel locus 5 on the travelplane 19. The drive controller 10 controls the travel driving unit 15while the drawing is executed. The mobile robot 100 at the forefront ofthe line having reached a predetermined position ends the basiccollection behavior shown in FIG. 9A.

In step S42, the detector 7 in each of the mobile robots 100 tracking atthe second and the subsequent positions in the line detects the travellocus 5 drawn on the travel plane 19.

Subsequently, in step S43, the drive controller 10 in each of the mobilerobots 100 tracking the detected travel locus 5 at the second and thesubsequent positions in the line tracking, controls the travel drivingunit 15 for tracking travel. The mobile robots 100 tracking at thesecond and the subsequent positions in the line then end the basiccollection behavior shown in FIG. 9A.

Described next is the specific example of the collection flow of thecollection system S100 for the plurality of mobile robots 100 executingtracking travel in the single line. FIG. 9B is a flowchart specificallyexemplifying the specific collection behavior. FIG. 9B exemplifies acase where the six mobile robots 100 eventually execute tracking travelin the single line.

Initially in step S1 “activate the mobile robots at the boarding gateA”, the collector 11 expected to collect the mobile robots 100 moves tothe location T1 as the boarding gate A and activates the drawing unit 6in the first mobile robot 101 and the detector 7 in the second mobilerobot 102 disposed at the location T1 as the boarding gate A to be readyfor starting drawing and detection.

Subsequently, in step S2, the collector 11 boards the first mobile robot101 and starts steering the first mobile robot 101 from the location T1as the boarding gate A toward the location T2 as the boarding gate B.When the first mobile robot 101 starts travelling, under the control ofthe drive controller 10, the drawing unit 6 in the first mobile robot101 causes the marker 6 b to start drawing to leave the travel locus 5on the travel plane 19, and executes drawing after the detector 7 findsthat there is no travel locus 5. Such behavior corresponds to thedrawing in step S41. The first mobile robot 101 subsequently executesonly the drawing in step S41 and needs to execute neither the detectionin step S42 nor the tracking in step S43.

In the second mobile robot 102 expected to track the first mobile robot101, the distance sensor 4 measures a distance to the first mobile robot101 positioned thereahead and transmits the measured distance to thecalculator 9 in the controller 14. The distance sensor 4 is activatedsimultaneously when the mobile robot 100 is activated. The distancesensor 4 having been activated constantly measures a distance at apredetermined period interval or the like and transmits a result of themeasurement to the calculator 9. The drive controller 10 can thusdetermine that this mobile robot 100 is not at the forefront of theline. When the calculator 9 determines that the measured distanceexceeds the distance X, the drive controller 10 receives information onthe determination from the calculator 9 and controls the travel drivingunit 15 such that the second mobile robot 102 continuously travelsstraight by the distance X from the current position (that is, theposition at the determination) until the detector 7 detects the travellocus 5.

The detector 7 in the second mobile robot 102 subsequently detects thetravel locus 5 of the first mobile robot 101 and the calculator 9calculates the travel locus 5 for tracking the first mobile robot 101 inaccordance with a result of the detection. The drive controller 10 drivecontrols the travel driving unit 15 in accordance with the calculatedtravel locus 5, so that the second mobile robot 102 tracks the travellocus 5.

The detection and the tracking correspond to the detection in step S42and the tracking in step S43. When the second mobile robot 102 tracksthe first mobile robot 101, the distance sensor 4 in the second mobilerobot 102 measures a distance to the preceding first mobile robot 101and the controller 14 controls to execute tracking travel until thedistance reaches a distance α. The distance α exceeds 0 cm and enablesthe distance sensor 4 in the second mobile robot 102 to detect the firstmobile robot 101 positioned thereahead. The distance α can have a fixednumerical value or a certain numerical range.

In the following description, similarly to the second mobile robot 102,the fourth mobile robot 104 tracking the third mobile robot 103 at theboarding gate B and the sixth mobile robot 106 tracking the fifth mobilerobot 105 at the boarding gate C execute tracking travel to have thedistance α from the preceding mobile robots 103 and 105, respectively.

In step S2 “steer the mobile robot to the boarding gate B” subsequent tostep S1, as shown in FIG. 10, the collector 11 continuously steers thefirst mobile robot 101 to a common passage T10 in the vicinity of thelocation T2 as the boarding gate B. The collector 11 stops the firstmobile robot 101 such that the mobile robots 101 and 102 align straighton the common passage T10 in the vicinity of the location T2 as theboarding gate B. The second mobile robot 102 travels to track thepreceding first mobile robot 101 with the distance α therebetween alongthe travel locus 5 drawn by the first mobile robot 101. The detectionand the tracking correspond to the detection in step S42 and thetracking in step S43.

The first mobile robot 101 executes only step S41 in the basic behaviorshown in FIG. 9A, whereas the second mobile robot 102 executes step S42and step S43 other than step S41 in the basic behavior shown in FIG. 9A.

In subsequent step S3 “activate the mobile robots at the boarding gateB”, the collector 11 temporarily leaves the first mobile robot 101 andboards the third mobile robot 103 as shown in FIG. 11. The collector 11then starts steering the third mobile robot 103 and manipulates theoperation unit 16 to move the third and fourth mobile robots 103 and 104at the location T2 as the boarding gate B as in step S1 and step S2 anddispose on the common passage T10 in the vicinity of the location T2 asthe boarding gate B such that the third and fourth mobile robots 103 and104 are disposed behind the second mobile robot 102 and are directedidentically and the first to fourth mobile robots 101 to 104 form asingle line.

Specifically, the collector 11 steers the third mobile robot 103 todispose the mobile robots 103 and 104 on the common passage T10 in thevicinity of the location T2 as the boarding gate B so that the detector7 in each of the mobile robots 103 and 104 can detect the travel locus 5drawn on the travel plane 19 by the drawing unit 6 in the first mobilerobot 101. The drive controller 10 subsequently activates the detector 7in each of the mobile robots 103 and 104. After the detector 7 isactivated, the collector 11 boards the first mobile robot 101 again torestart steering the first mobile robot 101 on the common passage T10toward the location T3 as the boarding gate C. The first mobile robot101 thereafter executes only step S41 in the basic behavior shown inFIG. 9A, whereas the second to fourth mobile robots 102 to 104 executestep S42 and step S43 other than step S41 in the basic behavior shown inFIG. 9A.

The mobile robots 103 and 104 can be disposed not in accordance withmanipulation of the operation unit 16 by the collector 11 but by meansof a remote device configured to remotely steer the mobile robots 103and 104.

In subsequent step S4 “steer the mobile robot to the boarding gate C”,as shown in FIG. 12, the collector 11 continuously steers the firstmobile robot 101 to the common passage T10 in the vicinity of thelocation T3 as the boarding gate C. The collector 11 stops the firstmobile robot 101 such that the mobile robots 101 to 104 align straighton the common passage T10 in the vicinity of the location T3 as theboarding gate C. The third and fourth mobile robots 103 and 104 travelto track the preceding second mobile robot 102 or the third mobile robot103 with the distance α therebetween along the travel locus 5 drawn bythe first mobile robot 101. The detection and the tracking correspond tothe detection in step S42 and the tracking in step S43.

In this manner, the third and fourth mobile robots 103 and 104 executestep S42 and step S43 other than step S41 in the basic behavior shown inFIG. 9A.

In subsequent step S5 “activate the mobile robots at the boarding gateC”, the collector 11 temporarily leaves the first mobile robot 101 andboards the fifth mobile robot 105 as shown in FIG. 13. The collector 11starts steering the fifth mobile robot 105 and manipulates the operationunit 16 to move the mobile robots 105 and 106 at the location T3 as theboarding gate C as in step S1 and step S2 and dispose on the commonpassage T10 in the vicinity of the location T3 as the boarding gate Csuch that the mobile robots 105 and 106 are disposed behind the fourthmobile robot 104 and are directed identically and the first to sixthmobile robots 101 to 106 form a single line.

Specifically, the collector 11 steers the fifth mobile robot 105 todispose the mobile robots 105 and 106 on the common passage T10 in thevicinity of the location T3 as the boarding gate C so that the detector7 in each of the mobile robots 105 and 106 can detect the travel locus 5drawn on the travel plane 19 by the drawing unit 6 in the first mobilerobot 101. The drive controller 10 activates the detector 7 in each ofthe mobile robots 105 and 106. After the detector 7 is activated, thecollector 11 boards the first mobile robot 101 again to restart steeringthe first mobile robot 101 toward the collection site T4. The firstmobile robot 101 thereafter executes only step S41 in the basic behaviorshown in FIG. 9A, whereas the second to sixth mobile robots 102 to 106execute step S42 and step S43 other than step S41 in the basic behaviorshown in FIG. 9A.

In subsequent step S6 “steer the mobile robot to the collection site”,as shown in FIG. 14, the collector 11 continuously steers the firstmobile robot 101 to the collection site T4. As shown in FIG. 15, thecollector 11 stops the first mobile robot 101 such that the first tosixth mobile robots 101 to 106 align straight to be collected at thecollection site T4. The third to sixth mobile robots 103 to 106 travelto track the preceding second mobile robot 102, the third mobile robot103, the fourth mobile robot 104, or the fifth mobile robot 105 with thedistance α therebetween along the travel locus 5 drawn by the firstmobile robot 101. The detection and the tracking correspond to thedetection in step S42 and the tracking in step S43.

In subsequent step S7 “store the mobile robots”, the collector 11manipulates the operation unit 16 to move the first to sixth mobilerobots 101 to 106 from the collection site T4 to a storage site T11.

As exemplarily shown in FIG. 16, the collector 11 initially manipulatesthe operation unit 16 to cause the drive controller 10 to stop drawingby the drawing unit 6 in the first mobile robot 101, and manipulates theoperation unit 16 to move the first mobile robot 101 to the storage siteT11. The second to sixth mobile robots 102 to 106 travel forward untilthe detector 7 in the second mobile robot 102 becomes unable to detectthe travel locus 5 drawn by the drawing unit 6 in the first mobile robot101.

As shown in FIG. 17, the drive controller 10 subsequently stopsdetection by the detector 7 in the second mobile robot 102, and thecollector 11 manipulates the operation unit 16 to move the second mobilerobot 102 to the storage site T11. The third to sixth mobile robots 103to 106 travel forward until the detector 7 in the third mobile robot 103becomes unable to detect the travel locus 5 drawn by the drawing unit 6in the first mobile robot 101. Such movement is repeated for each of thethird to fifth mobile robots 103 to 105.

As shown in FIG. 18, the drive controller 10 eventually stops detectionby the detector 7 in the sixth mobile robot 106, and the collector 11manipulates the operation unit 16 to move the sixth mobile robot 106 tothe storage site T11. The first mobile robot 101 is moved initially and

the remaining mobile robots are moved sequentially in the above example.The present embodiment is not limited in the order of moving the mobilerobots, and any appropriate one of the second to sixth mobile robots 102to 106 can be moved initially in place of the first mobile robot 101.

As described above, in tracking travel of the plurality of mobile robots100, the drawing unit 6 in the mobile robot 100 at the forefront of theline draws the travel locus 5 on the travel plane 19, the detector 7 inthe tracking mobile robot 100 detects the drawn travel locus 5, and thedrive controller 10 controls the tracking mobile robots 100 to travelalong the detected travel locus 5. Accordingly, tracking control alongthe identical travel locus 5 of the plurality of mobile robots 100 isachieved even in a broad space such as an air terminal including no wallor the like where the mobile robots 100 cannot recognize own positions.

Second Embodiment

Described next with reference to FIG. 19 is a collection system S200adopting tracking control of six mobile robots 200 according to thesecond embodiment of the present disclosure. For convenience in thedescription, the six mobile robots 200 will be denoted by a first mobilerobot 201, a second mobile robot 202, a third mobile robot 203, a fourthmobile robot 204, a fifth mobile robot 205, and a sixth mobile robot206.

Briefly, the collection system S200 is achieved by the mobile robots 200each including the constituent elements according to the firstembodiment as well as an eraser 8 configured to erase the travel locus 5drawn on the travel plane 19.

FIG. 19 is a schematic explanatory view from the top of the mobile robot200 according to the second embodiment of the present disclosure. Themobile robot 200 includes the mobile robot body 1, the drawing unit 6,the detector 7, the travel driving unit 15, the controller 14 includingthe drive controller 10, and the eraser 8. The constituent elementsidentical with those included in the mobile robot 100 will be denoted bythe identical reference signs and will not repeatedly be described indetail.

The eraser 8 is provided at the mobile robot body 1 and erases thetravel locus 5 drawn on the travel plane 19 by the drawing unit 6.

The controller 14 is connected to the drawing unit 6, the detector 7,and the eraser 8, and independently controls drawing by the drawing unit6, detection by the detector 7, and erasing by the eraser 8.

FIG. 20 is a schematic sectional view from a side of the mobile robot200. The drawing unit 6 and the detector 7 are configured and functionsimilarly to those of the mobile robot 100.

The drawing unit 6 adopts paint in a case where the travel plane 19 is ahard tile. Examples of the paint include paint that is completelyvolatilized to disappear by frictional heat. Such paint is specificallyexemplified by friction erasable ink having the commercial name “METAMOCOLOR” sold by PILOT CORPORATION.

FIGS. 21A and 21B are detailed views of the eraser 8. FIG. 21A is a planview from the top of the mobile robot 200, of the eraser 8, whereas FIG.21B is a perspective view from the bottom of the mobile robot 200, ofthe eraser 8.

The eraser 8 includes an expandable portion 8 a configured to be axiallyexpandable (e.g. vertically in FIG. 21B), a resin portion 8 b fixed at adistal end (e.g. the lower end in FIG. 21B) of the expandable portion 8a and having a projecting end, and an eraser driver 8 g like a motorconfigured to axially move the resin portion 8 b via the expandableportion 8 a and drive-controlled by the drive controller 10.

When the eraser 8 is activated, under control of the drive controller10, the eraser driver 8 g like a motor lowers the resin portion 8 b toextend the expandable portion 8 a axially downward and thus, the lowerend of the resin portion 8 b comes into direct contact with the travelplane 19. The resin portion 8 b is made of a material exemplified byelastomer and specifically exemplified by friction eraser sold by PILOTCORPORATION.

When the mobile robot 200 travels with the eraser 8 being activated andthe lower end of the resin portion 8 b being in direct contact with thetravel plane 19, the travel plane 19 and the resin portion 8 b havefriction therebetween to generate heat that volatilizes the paint of thetravel locus 5 drawn on the travel plane 19 to completely erase thetravel locus 5.

When the mobile robot 200 stops or the eraser 8 stops erasing, undercontrol of the drive controller 10, the eraser driver 8 g like a motorraises the resin portion 8 b to contract the expandable portion 8 a soas to prevent the resin portion 8 b from directly contacting the travelplane 19.

The eraser 8 described above is configured correspondingly to the casewhere the travel locus 5 is drawn with paint.

In another case where the travel locus 5 is drawn with particles, theeraser 8 can be configured as follows. As another example, the eraser 8alternatively includes a sucking device 8 h disposed in series in thetravel direction with the elements such as the eraser driver 8 g andconfigured to suck the particles applied onto the travel plane 19. Thesucking device 8 h sucks the particles to completely erase the travellocus 5. The eraser 8 selects how to erase the travel locus 5,specifically, which one to drive the sucking device 8 h or the eraserdriver 8 g, in accordance with a result of determination by the travelplane determiner 21.

As shown in FIG. 21C, the sucking device 8 h includes a nozzle 81, adust box 82, a first filter 83, a dust collecting blade 84, a motor 85,and a second filter 86. The motor 85 rotates the dust collecting blade84 to cause the particles configuring the travel locus 5 to be suckedthrough the nozzle 81 into the dust box 82. The first filter 83 catchesmost of the particles that are stored in the dust box 82. The secondfilter 86 catches fine particles having passed through the first filter83.

FIG. 22 depicts a positional relationship among the drawing unit 6, thedetector 7, and the eraser 8 included in the mobile robot 200. Thedrawing unit 6, the detector 7, and the eraser 8 are disposed in seriesin the travel direction. For example, the detector 7, the drawing unit6, and the eraser 8 are disposed in the mentioned order from ahead tobehind in the travel direction. Assume that the drawing unit 6 and thedetector 7 are disposed apart from each other by a distance Y and thedetector 7 and the eraser 8 are disposed apart from each other by adistance L.

FIG. 23 is a view depicting a state where the six mobile robots, namely,the first to sixth mobile robots 201 to 206 are disposed at thelocations T1 to T3 in the collection system S200. The two mobile robots,namely, the first mobile robot 201 and the second mobile robot 202 aredisposed next to each other at the location T1 as the boarding gate Aand are directed identically in the anteroposterior direction. The firstmobile robot 201 is disposed ahead in the travel direction and thesecond mobile robot 202 is disposed behind in the travel direction ofthe first mobile robot 201. Similarly, the two mobile robots, namely,the third mobile robot 203 and the fourth mobile robot 204 are disposednext to each other at the location T2 as the boarding gate B and aredirected identically in the anteroposterior direction. The third mobilerobot 203 is disposed ahead in the travel direction and the fourthmobile robot 204 is disposed behind in the travel direction of the thirdmobile robot 203. Similarly, the two mobile robots, namely, the fifthmobile robot 205 and the sixth mobile robot 206 are disposed next toeach other at the location T3 as the boarding gate C and are directedidentically in the anteroposterior direction. The fifth mobile robot 205is disposed ahead in the travel direction and the sixth mobile robot 206is disposed behind in the travel direction of the fifth mobile robot205.

FIG. 24 is a view of the collection site T4 for the six mobile robots,namely, the first to sixth mobile robots 201 to 206 in the collectionsystem S200. The first to sixth mobile robots 201 to 206 are collectedsequentially at the collection site T4 to form a single line such thatthe first mobile robot 201 is disposed at the forefront in the traveldirection.

FIG. 25 is a view depicting a positional relationship of the first tosixth mobile robots 201 to 206 disposed at the locations T1 to T3 as theboarding gates. A distance from the rear end of the mobile robot 201,203, or 205 disposed ahead at the location to the front end of themobile robot 202, 204, or 206 disposed behind will be referred to as aninter-robot distance, and the permissible maximum value of theinter-robot distance will be referred to as a maximum permissibleinter-robot distance D4. Assume that a distance X is obtained by addingthe distance D3 from the drawing unit 6 included in each of the mobilerobots 201 to 206 to the rear end of the mobile robot and the maximumpermissible inter-robot distance D4 to each other.

Described next is a collection flow of the collection system S200 for aplurality of mobile robots 200 executing tracking travel in a singleline. A specific example thereof will be described after description ofbasic behavior. FIG. 26A is a flowchart depicting the basic collectionbehavior.

Initially in step S50, when executing tracking travel in a single lineof a plurality of mobile robots 200, the drive controller 10 determineswhether or not the mobile robot 200 is at the forefront of the line.This determination can be made by the collector 11 who manipulates theoperation unit 16 to inform the drive controller 10 that this mobilerobot 200 is at the forefront of the line. The drive controller 10 canalternatively determine that this mobile robot 200 is at the forefrontof the line when the distance sensor 4 detects that there is no othermobile robot 200 ahead of this mobile robot 200 for a predeterminedperiod. The drive controller 10 can still alternatively determine thatthis mobile robot 200 is at the forefront of the line in an exemplarycase where the detector 7 detects no travel locus 5 even after thismobile robot 200 moves for a predetermined period or by a predetermineddistance.

The flow proceeds to step S51 if the drive controller 10 determines thatthis mobile robot 200 is at the forefront of the line. The flow proceedsto step S52 if the drive controller 10 determines that this mobile robot200 is not at the forefront of the line.

Subsequently, in step S51, the drive controller 10 controls to activatethe drawing unit 6 and the detector 7 in the mobile robot 200 at theforefront of the line so that the drawing unit 6 starts drawing thetravel locus 5 on the travel plane 19 and the detector 7 startsdetection. That is, drawing is executed after the detector 7 finds thatdrawing is not executed. The drive controller 10 controls the traveldriving unit 15 while the drawing and the detection are executed. Themobile robot 200 at the forefront of the line having reached apredetermined position ends the basic collection behavior shown in FIG.26A.

In step S52, the detector 7 in each of the mobile robots 200 tracking atthe second and the subsequent positions in the line detects the travellocus 5 drawn on the travel plane 19.

Subsequently, in step S53, the drive controller 10 in each of the mobilerobots 200 tracking the detected travel locus 5 at the second and thesubsequent positions in the line controls the travel driving unit 15 fortracking travel.

Subsequently, in step S54, it is determined whether or not the mobilerobot 200 is at the end of the line. In a case where the collector 11collecting the mobile robots 200 manipulates the operation unit 16 totransmit, to the drive controller 10, information that the mobile robot200 is at the end of the line, in step S55, the eraser 8 in the mobilerobot 200 at the end of the line erases the travel locus 5 and the drivecontroller 10 in the mobile robot 200 at the end of the line controlsthe travel driving unit 15 for tracking travel. The eraser 8 does notexecute erasing without such information. The mobile robots 200 trackingat the second and the subsequent positions in the line then end thebasic collection behavior shown in FIG. 26A.

Described next is the specific example of the collection flow of thecollection system S200 for the plurality of mobile robots 200 executingtracking travel in the single line. FIG. 265 is a flowchart depictingthe specific collection behavior. FIG. 26B exemplifies a case where thesix mobile robots 200 eventually execute tracking travel in the singleline.

Initially in step S21 “activate the mobile robots at the boarding gateA”, the collector 11 expected to collect the mobile robots 200 moves tothe location T1 as the boarding gate A, and activates the drawing unit 6in the first mobile robot 201 and the detector 7 and the eraser 8 in thesecond mobile robot 202 disposed at the location T1 as the boarding gateA to be ready for starting drawing and detection.

Subsequently, in step S22, the collector 11 boards the first mobilerobot 201 and starts steering the first mobile robot 201 from thelocation T1 as the boarding gate A toward the location T2 as theboarding gate B. When the first mobile robot 201 starts travelling,under the control of the drive controller 10, the drawing unit 6 in thefirst mobile robot 201 causes the marker 6 b to start drawing to leavethe travel locus 5 on the travel plane 19, and executes drawing afterthe detector 7 detects that there is no travel locus 5. Such behaviorcorresponds to the drawing in step S51. The first mobile robot 201subsequently executes only the drawing in step S51 and needs to executeneither the detection in step S52 nor the subsequent behavior.

In the second mobile robot 202 expected to track the first mobile robot201, the distance sensor 4 measures a distance to the first mobile robot201 positioned thereahead and transmits the distance to the calculator 9in the controller 14. The drive controller 10 can thus determine thatthis mobile robot 200 is not at the forefront of the line. When thecalculator 9 determines that the measured distance exceeds the distanceX, the drive controller 10 receives information on the determinationfrom the calculator 9 and controls the travel driving unit 15 such thatthe second mobile robot 202 continuously travels straight by thedistance X from the current position until the detector 7 detects thetravel locus 5.

In order to achieve control of the travel driving unit 15 by the drivecontroller 10 for continuous straight travel by the distance X, thedrive controller 10 has only to control the travel driving unit 15 suchthat the distance sensor 4 measures the distance to an identicalobstacle shortened by the distance X in the travel direction.Alternatively, the travel driving unit 15 may include the encoder 15 econfigured to detect rotational speed of the motor 15 m and the drivecontroller 10 controls the travel driving unit 15 such that a distanceobtained from the detected rotational speed is shortened by the distanceX. The collection system S100 according to the foregoing embodiment cansimilarly execute such control.

The detector 7 in the second mobile robot 202 subsequently detects thetravel locus 5 of the first mobile robot 201 and the calculator 9calculates the travel locus 5 for tracking the first mobile robot 201 inaccordance with a result of the detection. The drive controller 10 drivecontrols the travel driving unit 15 in accordance with the calculatedtravel locus 5, so that the second mobile robot 202 tracks the travellocus 5. The detection and the tracking correspond to the detection instep S52 and the tracking in step S53. The collector 11 manipulates theoperation unit 16 to transmit, to the drive controller 10, informationthat the second mobile robot 202 is at the end of the line duringtracking. The eraser 8 in the second mobile robot 202 accordingly erasesthe detected travel locus 5. Such behavior corresponds to the line endchecking in step S54 and the erasing in step S55. When the second mobilerobot 202 tracks the first mobile robot 201, the distance sensor 4 inthe second mobile robot 202 measures a distance to the preceding firstmobile robot 201 and the controller 14 controls to execute trackingtravel such the distance is equal to the distance α. The distance α issimilar to the distance α exemplified earlier.

In the following description, similarly to the second mobile robot 202,the fourth mobile robot 204 tracking the third mobile robot 203 at theboarding gate B and the sixth mobile robot 206 tracking the fifth mobilerobot 205 at the boarding gate C execute tracking travel to have thedistance α from the preceding mobile robots 203 and 205, respectively.

In step S22 “steer the mobile robot to the boarding gate B” subsequentto step S21, as shown in FIG. 27, the collector 11 continuously steersthe first mobile robot 201 to the common passage T10 in the vicinity ofthe location T2 as the boarding gate B. The collector 11 stops the firstmobile robot 201 such that the mobile robots 201 and 202 align straighton the common passage T10 in the vicinity of the location T2 as theboarding gate B. The second mobile robot 202 travels to track thepreceding first mobile robot 201 with the distance α therebetween on thetravel locus 5 drawn by the first mobile robot 201. The detection andthe tracking correspond to the detection in step S52 and the tracking instep S53. The travel locus 5 is completely erased by the activatederaser 8 in the second mobile robot 202. The line end checking and theerasing correspond to the line end checking in step S54 and the erasingin step S55.

The first mobile robot 201 executes only step S51 in the basic behaviorshown in FIG. 26A, whereas the second mobile robot 202 executes step S52and the subsequent steps other than step S51 in the basic behavior shownin FIG. 26A.

In subsequent step S23 “activate the mobile robots at the boarding gateB”, the collector 11 temporarily leaves the first mobile robot 201 andboards the third mobile robot 203 as shown in FIG. 28. The collector 11manipulates the operation unit 16 to cause the drive controller 10 tostop erasing by the eraser 8 in the second mobile robot 202. Thecollector 11 then starts steering the third mobile robot 203 andmanipulates the operation unit 16 to move the third and fourth mobilerobots 203 and 204 at the location T2 as the boarding gate B as in stepS21 and step S22 and dispose on the common passage T10 in the vicinityof the location T2 as the boarding gate B such that the third and fourthmobile robots 203 and 204 are disposed behind the second mobile robot202 and are directed identically and the first to fourth mobile robots201 to 204 form a single line.

Specifically, the collector 11 steers the third mobile robot 203 todispose the mobile robots 203 and 204 on the common passage T10 in thevicinity of the location T2 as the boarding gate B so that the detector7 in each of the mobile robots 203 and 204 can detect the travel locus 5drawn on the travel plane 19 by the drawing unit 6 in the first mobilerobot 201. Then, the drive controller 10 activates the detector 7 ineach of the mobile robots 203 and 204. Thereafter, the collector 11manipulates the operation unit 16 to cause the drive controller 10 ineach of the disposed mobile robots to activate the drawing unit 6 andthe detector 7 in the third mobile robot 203 and activate the detector 7and the eraser 8 in the fourth mobile robot 204. After these units areactivated, the collector 11 boards the first mobile robot 201 again torestart steering the first mobile robot 201 on the common passage T10toward the location T3 as the boarding gate C. The first mobile robot201 thereafter executes only step S51 in the basic behavior shown inFIG. 26A, whereas the second to fourth mobile robots 202 to 204 executestep S52 and step S53 other than step S51 in the basic behavior shown inFIG. 26A. The fourth mobile robot 204 further executes step S54 and stepS55 in the basic behavior shown in FIG. 26A.

After these units (namely, the drawing unit 6, the detector 7, and theeraser 8) are activated, the collector 11 boards the first mobile robot201 again to restart steering the first mobile robot 201 on the commonpassage T10 toward the location T3 as the boarding gate C. The third andfourth mobile robots 203 and 204 continuously travel straight by thedistance X until the detectors 7 each detect the travel locus 5, and thedrive controller 10 in the third mobile robot 203 automatically stopsdrawing by the drawing unit 6 when the third mobile robot 203 travels bythe distance Y after the detector 7 detects the travel locus 5. In orderto cause the drive controller 10 to automatically stop the drawing unit6 after travel by the distance Y, the drive controller 10 has only tostop the drawing unit 6 after the drive controller 10 controls thetravel driving unit 15 such that the distance sensor 4 measures thedistance to an identical obstacle shortened by the distance Y in thetravel direction. Alternatively, the travel driving unit 15 may includethe encoder 15 e configured to detect rotational speed of the motor 15m, the drive controller 10 controls the travel driving unit 15 such thata travel distance of the mobile robot 200 obtained from the detectedrotational speed is shortened by the distance Y, and the drivecontroller 10 then stops the drawing unit 6.

In subsequent step S24 “steer the mobile robot to the boarding gate C”,as shown in FIG. 29, the collector 11 continuously steers the firstmobile robot 201 to the common passage T10 in the vicinity of thelocation T3 as the boarding gate C. The collector 11 stops the firstmobile robot 201 such that the mobile robots 201 to 204 align straighton the common passage T10 in the vicinity of the location T3 as theboarding gate C. The third and fourth mobile robots 203 and 204 travelto track the preceding second mobile robot 202 or the third mobile robot203 with the distance α therebetween along the travel locus 5 drawn bythe first mobile robot 201. The detection and the tracking correspond tothe detection in step S52 and the tracking in step S53.

In this manner, the third and fourth mobile robots 203 and 204 executestep S52 and step S53 other than step S51 in the basic behavior shown inFIG. 26A.

The travel locus 5 is completely erased by the activated eraser 8 in thefourth mobile robot 204. Such behavior corresponds to step S54 and stepS55 in the basic behavior shown in FIG. 26A.

In subsequent step S25 “activate the mobile robots at the boarding gateC”, the collector 11 temporarily leaves the first mobile robot 201 andboards the fifth mobile robot 205 as shown in FIG. 30. The collector 11manipulates the operation unit 16 to cause the drive controller 10 tostop the eraser 8 in the fourth mobile robot 204. The collector 11starts steering the fifth mobile robot 205 and manipulates the operationunit 16 to move the mobile robots 205 and 206 at the location T3 as theboarding gate C as in step S21 and step S22 and dispose on the commonpassage T10 in the vicinity of the location T3 as the boarding gate Csuch that the mobile robots 205 and 206 are disposed behind the fourthmobile robot 204 and are directed identically and the first to sixthmobile robots 201 to 206 form a single line.

Specifically, the collector 11 steers the fifth mobile robot 205 todispose the mobile robots 205 and 206 on the common passage T10 in thevicinity of the location T3 as the boarding gate C so that the detector7 in each of the mobile robots 205 and 206 can detect the travel locus 5drawn on the travel plane 19 by the drawing unit 6 in the first mobilerobot 201, in other words, such that the mobile robots 204 to 206 alignstraight.

The collector 11 then activates the drawing unit 6 and the detector 7 inthe fifth mobile robot 205 and activates the detector 7 and the eraser 8in the sixth mobile robot 206.

After these units (namely, the drawing unit 6, the detector 7, and theeraser 8) are activated, the collector 11 boards the first mobile robot201 again to restart steering the first mobile robot 201 toward thecollection site T4. The mobile robots 205 and 206 continuously travelstraight by the distance X until the detectors 7 each detect the travellocus 5, and the drive controller 10 in the fifth mobile robot 205automatically stops the drawing unit 6 when the fifth mobile robot 205travels by the distance Y after the detector 7 detects the travel locus5.

The fifth and sixth mobile robots 205 and 206 subsequently execute stepS52 and step S53 other than step S51 in the basic behavior shown in FIG.26A. The sixth mobile robot 206 further executes step S54 and step S55in the basic behavior shown in FIG. 26A.

In subsequent step S26 “steer the mobile robot to the collection site”,as shown in FIG. 31, the collector 11 continuously steers the firstmobile robot 201 to the common passage T10 in the vicinity of thecollection site T4. As shown in FIG. 32, the collector 11 stops thefirst mobile robot 201 such that the first to sixth mobile robots 201 to206 align straight to be collected at the collection site T4. The thirdto sixth mobile robots 203 to 206 travel to track the preceding secondmobile robot 202, the third mobile robot 203, the fourth mobile robot204, or the fifth mobile robot 205 with the distance α therebetweenalong the travel locus 5 drawn by the first mobile robot 201. Thedetection and the tracking correspond to the detection in step S52 andthe tracking in step S53.

In subsequent step S27 “store the mobile robots”, the collector 11manipulates the operation unit 16 to move the first to sixth mobilerobots 201 to 206 from the collection site T4 to a storage site T11.

As exemplarily shown in FIG. 33, the collector 11 initially manipulatesthe operation unit 16 to cause the drive controller 10 to stop drawingby the drawing unit 6 in the first mobile robot 201, and manipulates theoperation unit 16 to move the first mobile robot 201 to the storage siteT11. The second to sixth mobile robots 202 to 206 travel forward untilthe detector 7 in the second mobile robot 202 becomes unable to detectthe travel locus 5 drawn by the drawing unit 6 in the first mobile robot201.

As shown in FIG. 34, the drive controller 10 subsequently stopsdetection by the detector 7 in the second mobile robot 202, and thecollector 11 manipulates the operation unit 16 to move the second mobilerobot 202 to the storage site T11. The third to sixth mobile robots 203to 206 travel forward until the detector 7 in the third mobile robot 203becomes unable to detect the travel locus 5 drawn by the drawing unit 6in the first mobile robot 201. Such movement is repeated for each of thethird to fifth mobile robots 203 to 205.

As shown in FIG. 35, when the sixth mobile robot 206 eventually travelsforward and stops where no travel locus 5 is detected, the collector 11causes the drive controller 10 to stop detection by the detector 7 andmanipulates the operation unit 16 to move forward the sixth mobile robot206 by the distance L.

The drive controller 10 then stops the eraser 8, and the collector 11manipulates to move the sixth mobile robot 206 to the collection siteT4. The travel locus 5 is completely erased by the activated eraser 8 inthe sixth mobile robot 206.

The first mobile robot 201 is moved initially and the remaining mobilerobots are moved sequentially in the above example. The presentembodiment is not limited in the order of moving the first to fifthmobile robots 201 to 205 as long as the sixth mobile robot 206 includingthe activated eraser 8 moves last.

As described above, the mobile robots 200 can move while the eraser 8 iserasing the travel locus 5 drawn on the travel plane 19. Thisconfiguration achieves tracking control of the plurality of mobilerobots 200 along the identical travel locus 5 that is not left on thetravel plane 19.

Third Embodiment

Described next with reference to FIG. 36 is a collection system S300adopting tracking control of six mobile robots 300 according to thethird embodiment of the present disclosure. For convenience in thedescription, the six mobile robots 300 will be denoted by a first mobilerobot 301, a second mobile robot 302, a third mobile robot 303, a fourthmobile robot 304, a fifth mobile robot 305, and a sixth mobile robot306.

Briefly, the collection system S300 is achieved by the mobile robots 300each including the constituent elements according to the secondembodiment and configured to automatically recognize the end of the linenot by the collector 11 but by the mobile robots 300.

FIG. 36 is a schematic explanatory view from the top of the mobile robot300 according to the third embodiment of the present disclosure.Similarly to the mobile robot 200 according to the second embodiment,the mobile robot 300 includes the mobile robot body 1, the drawing unit6, the detector 7, the travel driving unit 15, the controller 14including the drive controller 10, the eraser 8, as well as a reartracking determiner 12 configured to determine whether or not there isany mobile robot 200 tracking from behind. The constituent elementsidentical with those included in the mobile robot 100 or 200 will bedenoted by the identical reference signs and will not repeatedly bedescribed in detail. Examples of the rear tracking determiner 12, whichwill hereinafter be called the determiner 12, include an image sensorand any other element configured to recognize any mobile robot 300disposed behind the mobile robot 300 including the determiner 12executing determination. The determiner 12 exemplarily configured by animage sensor compares image information acquired by the image sensorwith information such as an outline or color of the mobile robot 300,determines whether or not there is any mobile robot 300, and transmits aresult of the determination to the drive controller 10 in the controller14. In a case where the determiner 12 determines that there is no mobilerobot 300 therebehind, the drive controller 10 in the controller 14activates the eraser 8. In another case where the determiner 12determines that there is the mobile robot 300 therebehind, thecontroller 14 does not activate the eraser 8.

In the collection flow according to the second embodiment, the collector11 manipulates the operation unit 16 every time to activate and stop theeraser 8 in the mobile robot 200 at the end of the line. In contrast,the present third embodiment achieves automatically activating andstopping the eraser 8 in accordance with a result of determination bythe controller 14. A specific collection flow according to the presentembodiment is similar to the collection flow according to the secondembodiment. The following will thus mainly mention differencestherebetween with reference to the collection flow shown in FIG. 37similar to the collection flow shown in FIG. 26B.

Initially in step S21A in FIG. 37 “activate the mobile robots at theboarding gate A”, as in FIG. 26B, the collector 11 expected to collectthe mobile robots 300 moves to the location T1 as the boarding gate Aand activates the drawing unit 6 in the mobile robot 301 and thedetector 7 in the second mobile robot 302 disposed at the location T1 asthe boarding gate A to be ready for starting drawing and detection. Thedeterminer 12 in the second mobile robot 302 constantly determineswhether or not there is any additional mobile robot 300 behind thesecond mobile robot 302 in accordance with a locus drawn by the drawingunit 6. If the determiner 12 in the second mobile robot 302 determinesthat there is no mobile robot 300 therebehind, the controller 14activates the eraser 8.

Subsequent step S22 in FIG. 37 is similar to step S22 in FIG. 26A, andthe collector 11 steers the mobile robot to the boarding gate B.

In subsequent step S23A in FIG. 37 “activate the mobile robots at theboarding gate B”, the collector 11 temporarily leaves the first mobilerobot 301 and boards the third mobile robot 303. The collector 11 thenmanipulates the operation unit 16 to cause the drive controller 10 tomove the third and fourth mobile robots 303 and 304 at the location T2as the boarding gate B as in step S21A and step S22 and dispose on thecommon passage T10 in the vicinity of the location T2 as the boardinggate B such that the third and fourth mobile robots 303 and 304 aredisposed behind the second mobile robot 302 and are directedidentically. If the determiner 12 in the second mobile robot 302determines that there is the additional mobile robot 300 behind thesecond mobile robot 302, the drive controller 10 in the second mobilerobot 302 stops the eraser 8. The determiner 12 in the second mobilerobot 302 constantly determines whether or not there is any additionalmobile robot 300 behind the second mobile robot 302. In a case where thethird mobile robot 303 moves to be disposed behind the second mobilerobot 302, the determiner 12 determines that there is the additionalmobile robot 300 behind the second mobile robot 302. The determiner 12transmits information on the determination to the drive controller 10that stops the eraser 8 in the second mobile robot 302.

Subsequent step S24 in FIG. 37 is similar to step S24 in FIG. 26A, andthe collector 11 steers the mobile robot to the boarding gate C.

In subsequent step S25A in FIG. 37 “activate the mobile robots at theboarding gate C”, the collector 11 temporarily leaves the first mobilerobot 301 and boards the fifth mobile robot 305. The collector 11manipulates the operation unit 16 to start steering the fifth mobilerobot 305 and manipulates the operation unit 16 to move the mobilerobots 305 and 306 at the location T3 as the boarding gate C as in stepS21A and step S22 and dispose on the common passage T10 in the vicinityof the location T3 as the boarding gate C such that the mobile robots305 and 306 are disposed behind the fourth mobile robot 304 and aredirected identically and the first to sixth mobile robots 301 to 306form a single line. The determiner 12 in the fourth mobile robot 304determines that there is the additional mobile robot 300 behind thefourth mobile robot 304, and the drive controller 10 stops the eraser 8.

Subsequent step S26 in FIG. 37 is similar to step S26 in FIG. 26A, andthe collector 11 steers the mobile robot to the collection site.

In subsequent step S27A in FIG. 37 “store the mobile robots”, when thedrive controller 10 stops the detector 7 in the sixth mobile robot 306at the end of the line, the collector 11 manipulates the operation unit16 to move forward the sixth mobile robot 306 by the distance L and thenmanipulates the operation unit 16 to cause the drive controller 10 tostop the eraser 8.

Assume that the determiner 12 is configured by an image sensor or thelike to detect and determine whether or not there is any other mobilerobot 300 therebehind and recognize whether or not the mobile robot 300is at the end of the line. The collector 11 can specify the mobile robot306 at the end of the line instead of detection with the image sensor orthe like. In such a case, there can be provided an input unit configuredto receive input of information by the collector 11 to cause the mobilerobot 306 at the end of the line to recognize as being at the end of theline.

As described above, the controller 14 can activate the eraser 8 in acase where the determiner 12 thus provided determines that there is nomobile robot 300 therebehind. In another case where the determiner 12determines that there is the mobile robot therebehind, the controller 14can cause the drive controller 10 to stop the eraser 8. Thisconfiguration achieves reduction in workload of the collector 11 as wellas tracking control of the plurality of mobile robots 300 along theidentical travel locus 5 that is not left on the travel plane 19.

The present disclosure has been described by exemplifying the first tothird embodiments and the modification examples. The present disclosureis obviously not limited to the first to third embodiments or themodification examples. The present disclosure is also applicable to thefollowing modes.

Part or entirety of each of the controllers 14 like the drive controller10 is specifically configured by a computer system including amicroprocessor, a ROM, a RAM, a hard disk unit, a display unit, akeyboard, a mouse, and the like. The RAM or the hard disk unit stores acomputer program. The controllers 14 each achieve the function when themicroprocessor operates in accordance with the computer program. Thecomputer program includes a plurality of command codes indicatingcommands to a computer for achievement of a predetermined function.

The constituent elements are each achieved by causing a program executorlike a CPU to read and execute a software program stored in a recordingmedium such as a hard disk or a semiconductor memory.

Software achieving part or entirety of the elements in the controller 14according to any one of the embodiments and the modification examples isa program relevant to a method of tracking a mobile robot according tothe following aspects. Specifically, this program is a control programrelevant to a method of tracking a mobile robot for causing a computerto execute the following control or the following determination.

This program can be downloaded from a server or the like to be executed,or can be read from a predetermined recording medium (e.g. an opticaldisk like a CD-ROM, a magnetic disk, or a semiconductor memory)preliminarily storing the program.

This program can be executed by a single or a plurality of computers. Inother words, the program can be processed in a centralized ordecentralized manner.

The embodiments of the present disclosure have been described in detailabove with reference to the drawings, and various aspects of the presentdisclosure will be described below.

According to a first aspect of the present disclosure, there is provideda mobile robot comprising:

a mobile robot body;

a drawing unit provided at the mobile robot body and including a markerconfigured to draw a travel locus of the mobile robot on a travel plane;

a detector provided at the mobile robot body and configured to detectthe travel locus drawn by the drawing unit;

a travel driving unit configured to drive to move the mobile robot body;and

a drive controller configured to drive control the travel driving unitsuch that the mobile robot body travels along the travel locus detectedby the detector.

According to a second aspect of the present disclosure, there isprovided the mobile robot according to the first aspect, wherein thedrawing unit and the detector are disposed in series in the mobile robotbody in a travel direction of the mobile robot and the drawing unit ispositioned ahead of the detector.

According to a third aspect of the present disclosure, there is providedthe mobile robot according to the first or second aspect, furthercomprising an eraser provided at the mobile robot body and configured toerase the travel locus drawn on the travel plane by the drawing unit.

According to a fourth aspect of the present disclosure, there isprovided the mobile robot according to the third aspect, furthercomprising

a determiner provided at the mobile robot body and configured todetermine whether or not the mobile robot is at an end of a line inaccordance with information on whether or not there is any mobile robotbehind the mobile robot body,

wherein when the determiner determines that the mobile robot is at theend of the line, the erasers erases the travel locus drawn on the travelplane by the drawing unit.

According to a fifth aspect of the present disclosure, there is providedthe mobile robot according to any one of the first to fourth aspects,

assuming that the drawing unit including the marker is referred to as afirst drawing unit,

the mobile robot further comprising:

a second drawing unit provided at the mobile robot body and including aparticle discharge mechanism configured to scatter particles to draw thetravel locus of the mobile robot on the travel plane; and

a travel plane determiner provided at the mobile robot body andconfigured to detect and determine a type of the travel plane,

wherein the first drawing unit or the second drawing unit is selectivelydriven in accordance with a result of determination by the travel planedeterminer.

According to a sixth aspect of the present disclosure, there is provideda method of tracking a mobile robot when a plurality of mobile robots,each configured identically to the mobile robot according to anyone ofthe first to fifth aspects, executes tracking travel in a single line,the method comprising:

determining whether each of the mobile robots is at a forefront of theline;

in a first case where the mobile robot is at the forefront of the line,moving the mobile robot at the forefront of the line while drawing thetravel locus on the travel plane by the drawing unit; and

in a second case where the mobile robot is not at the forefront of theline but is tracking, detecting the travel locus drawn on the travelplane by the detector in the tracking mobile robot; and tracking thedetected travel locus by the tracking mobile robot to execute trackingtravel.

According to a seventh aspect of the present disclosure, there isprovided the method of tracking a mobile robot according to the sixthaspect, when a plurality of mobile robots, each configured identicallyto the mobile robot according to the fourth aspect, executes trackingtravel in a single line, the method comprising:

determining whether each of the mobile robots is at a forefront of theline;

in a first case where the mobile robot is at the forefront of the line,moving the mobile robot at the forefront of the line while drawing thetravel locus on the travel plane by the drawing unit; and

in a second case where the mobile robot is not at the forefront of theline but is tracking, tracking while detecting the travel locus by thedetector in the tracking mobile robot; and determining by the determinerprovided at the mobile robot body whether the mobile robot is at an endof the line, and when the determiner determines that the mobile robot isat the end of the line, executing tracking travel while erasing thetravel locus by the eraser in the mobile robot at the end of the line.

Any of the various embodiments and the modification examples can beappropriately combined to achieve effects thereof. The presentdisclosure is applicable to appropriate combination among theembodiments, appropriate combination among the examples, appropriatecombination among the embodiments and the examples, as well asappropriate combination of different features in the embodiments or theexamples.

The mobile robot and the method of tracking the mobile robot accordingto any one of the aspects of the present disclosure are applicable tosimultaneous collection of a plurality of mobile robots each loadingcargo or a person in a large facility such an air terminal.

1. A mobile robot comprising: a mobile robot body; a drawing unit provided at the mobile robot body and including a marker configured to draw a travel locus of the mobile robot on a travel plane; a detector provided at the mobile robot body and configured to detect the travel locus drawn by the drawing unit; a travel driving unit configured to drive to move the mobile robot body; and a drive controller configured to drive control the travel driving unit such that the mobile robot body travels along the travel locus detected by the detector.
 2. The mobile robot according to claim 1, wherein the drawing unit and the detector are disposed in series in the mobile robot body in a travel direction of the mobile robot and the drawing unit is positioned ahead of the detector.
 3. The mobile robot according to claim 1, further comprising an eraser provided at the mobile robot body and configured to erase the travel locus drawn on the travel plane by the drawing unit.
 4. The mobile robot according to claim 2, further comprising an eraser provided at the mobile robot body and configured to erase the travel locus drawn on the travel plane by the drawing unit.
 5. The mobile robot according to claim 3, further comprising a determiner provided at the mobile robot body and configured to determine whether or not the mobile robot is at an end of a line in accordance with information on whether or not there is any mobile robot behind the mobile robot body, wherein when the determiner determines that the mobile robot is at the end of the line, the erasers erases the travel locus drawn on the travel plane by the drawing unit.
 6. The mobile robot according to claim 1, assuming that the drawing unit including the marker is referred to as a first drawing unit, the mobile robot further comprising: a second drawing unit provided at the mobile robot body and including a particle discharge mechanism configured to scatter particles to draw the travel locus of the mobile robot on the travel plane; and a travel plane determiner provided at the mobile robot body and configured to detect and determine a type of the travel plane, wherein the first drawing unit or the second drawing unit is selectively driven in accordance with a result of determination by the travel plane determiner.
 7. The mobile robot according to claim 2, assuming that the drawing unit including the marker is referred to as a first drawing unit, the mobile robot further comprising: a second drawing unit provided at the mobile robot body and including a particle discharge mechanism configured to scatter particles to draw the travel locus of the mobile robot on the travel plane; and a travel plane determiner provided at the mobile robot body and configured to detect and determine a type of the travel plane, wherein the first drawing unit or the second drawing unit is selectively driven in accordance with a result of determination by the travel plane determiner.
 8. The mobile robot according to claim 3, assuming that the drawing unit including the marker is referred to as a first drawing unit, the mobile robot further comprising: a second drawing unit provided at the mobile robot body and including a particle discharge mechanism configured to scatter particles to draw the travel locus of the mobile robot on the travel plane; and a travel plane determiner provided at the mobile robot body and configured to detect and determine a type of the travel plane, wherein the first drawing unit or the second drawing unit is selectively driven in accordance with a result of determination by the travel plane determiner.
 9. The mobile robot according to claim 5, assuming that the drawing unit including the marker is referred to as a first drawing unit, the mobile robot further comprising: a second drawing unit provided at the mobile robot body and including a particle discharge mechanism configured to scatter particles to draw the travel locus of the mobile robot on the travel plane; and a travel plane determiner provided at the mobile robot body and configured to detect and determine a type of the travel plane, wherein the first drawing unit or the second drawing unit is selectively driven in accordance with a result of determination by the travel plane determiner.
 10. A method of tracking a mobile robot when a plurality of mobile robots, each configured identically to the mobile robot according to claim 1, executes tracking travel in a single line, the method comprising: determining whether each of the mobile robots is at a forefront of the line; in a first case where the mobile robot is at the forefront of the line, moving the mobile robot at the forefront of the line while drawing the travel locus on the travel plane by the drawing unit; and in a second case where the mobile robot is not at the forefront of the line but is tracking, detecting the travel locus drawn on the travel plane by the detector in the tracking mobile robot; and tracking the detected travel locus by the tracking mobile robot to execute tracking travel.
 11. A method of tracking a mobile robot when a plurality of mobile robots, each configured identically to the mobile robot according to claim 2, executes tracking travel in a single line, the method comprising: determining whether each of the mobile robots is at a forefront of the line; in a first case where the mobile robot is at the forefront of the line, moving the mobile robot at the forefront of the line while drawing the travel locus on the travel plane by the drawing unit; and in a second case where the mobile robot is not at the forefront of the line but is tracking, detecting the travel locus drawn on the travel plane by the detector in the tracking mobile robot; and tracking the detected travel locus by the tracking mobile robot to execute tracking travel.
 12. A method of tracking a mobile robot when a plurality of mobile robots, each configured identically to the mobile robot according to claim 3, executes tracking travel in a single line, the method comprising: determining whether each of the mobile robots is at a forefront of the line; in a first case where the mobile robot is at the forefront of the line, moving the mobile robot at the forefront of the line while drawing the travel locus on the travel plane by the drawing unit; and in a second case where the mobile robot is not at the forefront of the line but is tracking, detecting the travel locus drawn on the travel plane by the detector in the tracking mobile robot; and tracking the detected travel locus by the tracking mobile robot to execute tracking travel.
 13. A method of tracking a mobile robot when a plurality of mobile robots, each configured identically to the mobile robot according to claim 5, executes tracking travel in a single line, the method comprising: determining whether each of the mobile robots is at a forefront of the line; in a first case where the mobile robot is at the forefront of the line, moving the mobile robot at the forefront of the line while drawing the travel locus on the travel plane by the drawing unit; and in a second case where the mobile robot is not at the forefront of the line but is tracking, detecting the travel locus drawn on the travel plane by the detector in the tracking mobile robot; and tracking the detected travel locus by the tracking mobile robot to execute tracking travel.
 14. A method of tracking a mobile robot when a plurality of mobile robots, each configured identically to the mobile robot according to claim 6, executes tracking travel in a single line, the method comprising: determining whether each of the mobile robots is at a forefront of the line; in a first case where the mobile robot is at the forefront of the line, moving the mobile robot at the forefront of the line while drawing the travel locus on the travel plane by the drawing unit; and in a second case where the mobile robot is not at the forefront of the line but is tracking, detecting the travel locus drawn on the travel plane by the detector in the tracking mobile robot; and tracking the detected travel locus by the tracking mobile robot to execute tracking travel.
 15. The method of tracking a mobile robot according to claim 10, when a plurality of mobile robots executes tracking travel in a single line, each of the mobile robots comprises: a mobile robot body; a drawing unit provided at the mobile robot body and including a marker configured to draw a travel locus of the mobile robot on a travel plane; a detector provided at the mobile robot body and configured to detect the travel locus drawn by the drawing unit; a travel driving unit configured to drive to move the mobile robot body; and a drive controller configured to drive control the travel driving unit such that the mobile robot body travels along the travel locus detected by the detector, wherein the drawing unit and the detector are disposed in series in the mobile robot body in a travel direction of the mobile robot and the drawing unit is positioned ahead of the detector, further comprising an eraser provided at the mobile robot body and configured to erase the travel locus drawn on the travel plane by the drawing unit, and a determiner provided at the mobile robot body and configured to determine whether or not the mobile robot is at an end of a line in accordance with information on whether or not there is any mobile robot behind the mobile robot body, wherein when the determiner determines that the mobile robot is at the end of the line, the erasers erases the travel locus drawn on the travel plane by the drawing unit, the method comprising: determining whether each of the mobile robots is at a forefront of the line; in a first case where the mobile robot is at the forefront of the line, moving the mobile robot at the forefront of the line while drawing the travel locus on the travel plane by the drawing unit; and in a second case where the mobile robot is not at the forefront of the line but is tracking, tracking while detecting the travel locus by the detector in the tracking mobile robot; and determining by the determiner provided at the mobile robot body whether the mobile robot is at an end of the line, and when the determiner determines that the mobile robot is at the end of the line, executing tracking travel while erasing the travel locus by the eraser in the mobile robot at the end of the line.
 16. The method of tracking a mobile robot according to claim 11, when a plurality of mobile robots, executes tracking travel in a single line, each of the mobile robots comprises: a mobile robot body; a drawing unit provided at the mobile robot body and including a marker configured to draw a travel locus of the mobile robot on a travel plane; a detector provided at the mobile robot body and configured to detect the travel locus drawn by the drawing unit; a travel driving unit configured to drive to move the mobile robot body; and a drive controller configured to drive control the travel driving unit such that the mobile robot body travels along the travel locus detected by the detector, wherein the drawing unit and the detector are disposed in series in the mobile robot body in a travel direction of the mobile robot and the drawing unit is positioned ahead of the detector, further comprising an eraser provided at the mobile robot body and configured to erase the travel locus drawn on the travel plane by the drawing unit, and a determiner provided at the mobile robot body and configured to determine whether or not the mobile robot is at an end of a line in accordance with information on whether or not there is any mobile robot behind the mobile robot body, wherein when the determiner determines that the mobile robot is at the end of the line, the erasers erases the travel locus drawn on the travel plane by the drawing unit, the method comprising: determining whether each of the mobile robots is at a forefront of the line; in a first case where the mobile robot is at the forefront of the line, moving the mobile robot at the forefront of the line while drawing the travel locus on the travel plane by the drawing unit; and in a second case where the mobile robot is not at the forefront of the line but is tracking, tracking while detecting the travel locus by the detector in the tracking mobile robot; and determining by the determiner provided at the mobile robot body whether the mobile robot is at an end of the line, and when the determiner determines that the mobile robot is at the end of the line, executing tracking travel while erasing the travel locus by the eraser in the mobile robot at the end of the line.
 17. The method of tracking a mobile robot according to claim 12, when a plurality of mobile robots, each of the mobile robots comprises: a mobile robot body; a drawing unit provided at the mobile robot body and including a marker configured to draw a travel locus of the mobile robot on a travel plane; a detector provided at the mobile robot body and configured to detect the travel locus drawn by the drawing unit; a travel driving unit configured to drive to move the mobile robot body; and a drive controller configured to drive control the travel driving unit such that the mobile robot body travels along the travel locus detected by the detector, wherein the drawing unit and the detector are disposed in series in the mobile robot body in a travel direction of the mobile robot and the drawing unit is positioned ahead of the detector, further comprising an eraser provided at the mobile robot body and configured to erase the travel locus drawn on the travel plane by the drawing unit, and a determiner provided at the mobile robot body and configured to determine whether or not the mobile robot is at an end of a line in accordance with information on whether or not there is any mobile robot behind the mobile robot body, wherein when the determiner determines that the mobile robot is at the end of the line, the erasers erases the travel locus drawn on the travel plane by the drawing unit, the method comprising: determining whether each of the mobile robots is at a forefront of the line; in a first case where the mobile robot is at the forefront of the line, moving the mobile robot at the forefront of the line while drawing the travel locus on the travel plane by the drawing unit; and in a second case where the mobile robot is not at the forefront of the line but is tracking, tracking while detecting the travel locus by the detector in the tracking mobile robot; and determining by the determiner provided at the mobile robot body whether the mobile robot is at an end of the line, and when the determiner determines that the mobile robot is at the end of the line, executing tracking travel while erasing the travel locus by the eraser in the mobile robot at the end of the line.
 18. The method of tracking a mobile robot according to claim 13, when a plurality of mobile robots, executes tracking travel in a single line, each of the mobile robots comprises: a mobile robot body; a drawing unit provided at the mobile robot body and including a marker configured to draw a travel locus of the mobile robot on a travel plane; a detector provided at the mobile robot body and configured to detect the travel locus drawn by the drawing unit; a travel driving unit configured to drive to move the mobile robot body; and a drive controller configured to drive control the travel driving unit such that the mobile robot body travels along the travel locus detected by the detector, wherein the drawing unit and the detector are disposed in series in the mobile robot body in a travel direction of the mobile robot and the drawing unit is positioned ahead of the detector, further comprising an eraser provided at the mobile robot body and configured to erase the travel locus drawn on the travel plane by the drawing unit, and a determiner provided at the mobile robot body and configured to determine whether or not the mobile robot is at an end of a line in accordance with information on whether or not there is any mobile robot behind the mobile robot body, wherein when the determiner determines that the mobile robot is at the end of the line, the erasers erases the travel locus drawn on the travel plane by the drawing unit, the method comprising: determining whether each of the mobile robots is at a forefront of the line; in a first case where the mobile robot is at the forefront of the line, moving the mobile robot at the forefront of the line while drawing the travel locus on the travel plane by the drawing unit; and in a second case where the mobile robot is not at the forefront of the line but is tracking, tracking while detecting the travel locus by the detector in the tracking mobile robot; and determining by the determiner provided at the mobile robot body whether the mobile robot is at an end of the line, and when the determiner determines that the mobile robot is at the end of the line, executing tracking travel while erasing the travel locus by the eraser in the mobile robot at the end of the line.
 19. The method of tracking a mobile robot according to claim 14, when a plurality of mobile robots, executes tracking travel in a single line, each of the mobile robots comprises: a mobile robot body; a drawing unit provided at the mobile robot body and including a marker configured to draw a travel locus of the mobile robot on a travel plane; a detector provided at the mobile robot body and configured to detect the travel locus drawn by the drawing unit; a travel driving unit configured to drive to move the mobile robot body; and a drive controller configured to drive control the travel driving unit such that the mobile robot body travels along the travel locus detected by the detector, wherein the drawing unit and the detector are disposed in series in the mobile robot body in a travel direction of the mobile robot and the drawing unit is positioned ahead of the detector, further comprising an eraser provided at the mobile robot body and configured to erase the travel locus drawn on the travel plane by the drawing unit, and a determiner provided at the mobile robot body and configured to determine whether or not the mobile robot is at an end of a line in accordance with information on whether or not there is any mobile robot behind the mobile robot body, wherein when the determiner determines that the mobile robot is at the end of the line, the erasers erases the travel locus drawn on the travel plane by the drawing unit, the method comprising: determining whether each of the mobile robots is at a forefront of the line; in a first case where the mobile robot is at the forefront of the line, moving the mobile robot at the forefront of the line while drawing the travel locus on the travel plane by the drawing unit; and in a second case where the mobile robot is not at the forefront of the line but is tracking, tracking while detecting the travel locus by the detector in the tracking mobile robot; and determining by the determiner provided at the mobile robot body whether the mobile robot is at an end of the line, and when the determiner determines that the mobile robot is at the end of the line, executing tracking travel while erasing the travel locus by the eraser in the mobile robot at the end of the line. 